Graphene: Quest for the Killer App

By Rosemarie Szostak, Ph.D., Nerac Analyst

Originally Published November 28, 2016

A killer app has to be exceptionally appealing, amazingly useful and totally simple. For example, the camera on a cell phone. Not only can you record a selfie, but you can post it on Facebook right from the phone. A material science killer app in the oil industry is the use of the aluminosilicate zeolite Y as a catalyst in petroleum refining. This material converts more of the barrel of crude oil into the high demand product, gasoline. If not for this killer app, the world would be awash in asphalt, and gasoline would cost a fortune. Researchers isolated a 2-dimensional sheet of the 12^th element of the periodic table from graphite called graphene, and both academic and industrial scientists have fantasized about applications in areas such as energy, aerospace, biomedical & life sciences, electronics, oil & gas, paints, coatings & adhesives, and defense. The hunt for the killer app for graphene was on.

Graphene, an allotrope of carbon, consists of a single atomic layer of carbon arranged in the form of a hexagonal honeycomb lattice. This material exhibits remarkable strength, flexibility, electrical conductivity and heat resistance in addition to being light weight.

Preparation of Graphene

Graphene can be produced through one of four general methods: a) mechanical exfoliation of graphite, b) chemically derived from graphite through oxidation/reduction process, c) chemical vapor deposition (CVD)/pulsed laser deposition (PLD) or related technologies, d) grown from SiC. Australia and China have quality deposits of graphite and are exploiting the mineral route. The challenge is that the graphene produced from graphite is limited to micron-size flakes. Silicon carbide route is limited by the price and size of a SiC wafer. At present, the deposition processes represent the most industrially scalable technology for large-area high-quality graphene. The price, however, is steep. Very steep.

There are three primary applications under intense investigation:

1. a) Replacement for Indium Tin Oxide (ITO) in touch displays
2. b) Heat spreader and thermal management
3. c) Batteries

There is reason for excitement, but there is also competition.

A replacement for Indium Tin Oxide (ITO) in touch displays

The dominant material in the area of transparent conductors, used in touch displays, is indium tin oxide (ITO). Finding a replacement for ITO represents an $8.1B market by 2021 and graphene has the potential to replace it. However, so do metal mesh, silver nanowires, conductive polymers, carbon nanotubes and other transparent conductive oxides. The graph below puts these materials in perspective relative to ITO. Even if graphene does decrease in price over time, it would still be in competition with other materials that provide the same function. Thus ITO replacement, though feasible, is not going to be the killer app.

From: Touch Display Research Inc. market report

A feature of graphene is flexibility, opening a world of potential applications that require flexibility along with conductivity and transparency. Suggested applications include flexible smartphones and computers, wearable electronics and medical devices. ITO is brittle and inflexible. However, metal mesh and silver nanowires are also flexible transparent conductors, thus there may be competition for graphene. Though a flexible smartphone sounds intriguing, the question remains whether one would have a need or desire to have a phone that bends. Marketing companies may find applications for bendable advertising displays, and it has been proposed that dashboards of automobiles will ultimately become a complete touch screen. This may be a gimmick that may also turn into a highly desirable convenience for drivers, but the challenge remains in the production of affordable large area graphene sheets. Thus a flexible transparent conductor, still may not represent the killer app for graphene.

Heat spreader and thermal management

Thermal management and high-flux cooling are the way a manufacturer regulates the unwanted heat caused by the normal functioning of an electronic system. Such system include field-effect transistors, integrated circuits, printed circuit boards, three-dimensional ICs, and optoelectronic devices, such as light-emitting diodes (LEDs), and related electronic, optoelectronic, and photonic devices and circuits. The market for thermal management is $11.2Billion in 2016 and expected to rise to $14.7Billion by 2021. In consumer products alone, the market is projected to grow at a five-year compound annual growth rate (CAGR) of 10.1%.

The requirements for a heat spreader include: a) higher thermal conductivity, b) optimum coefficient of thermal expansion, and c) good bondability between the semiconductor chip and solder.

Graphene is an order of magnitude better conductor of heat and is similar to carbon nanotubes. It also has a low heat of expansion, and therefore would be the preferred material for thermal spreading for electronic devices.

Cost is still a driver in thermal management and though graphene may open up new opportunities in high-power microelectronics, thermal management sadly remains an afterthought in electronics, optoelectronics and photonics development. Even so, its superior properties may ultimately be the enabler of that killer app.

Batteries

The thing we cannot live without. Lithium-ion batteries have become the standard go-to rechargeable power source from electronics to electric vehicles. The lithium ion battery market is huge, which is a driver for graphene as electrode material. By 2022 it is expected the lithium ion battery market will reach $46.21Billion with a CAGR of 10.8%. The goal is to improve capacity and recharge performance, and graphene has the potential to do both. This is projected to be the killer app, if successful, that would solve the problem of electric vehicle range and recharge time. At least that is hoped. If a graphene lithium ion battery can achieve 1,000Wh/kg (Li-ion is 180Wh/kg) and a 15-minute recharge with cycles greatly exceeding today’s lithium ion batteries, as is being hyped this year, it could be a game changer. The Chinese company, Dongxu Optoelectronics claims its newest battery regains its lost charge within 13-15 minutes. Though thinking about the Samsung Galaxy Note 7 fires recently, there are still significant challenges to overcome.

The challenge is that carbon black, as well as graphite, are competing for electrode materials in these batteries and, again, the cost of graphene, may be the limiting factor if the improvements are not as spectacular as hyped but merely modest.

The truth is out there

The quest continues for that killer app for graphene. The main focus of much of the R&D has been on the use of graphene as a substitute for other materials in present applications. Graphene may find its killer potential in something that has yet to be imagined or in a field that no one would have suspected, and where there is no present market for the application. But once accepted, it will become indispensable, like the camera on the smartphone. The challenge for the injection of any new material into an application is that there are both competing materials as well as competing technologies. The key for successful incorporation of a material such as graphene is whether it can ultimately compete on cost and uniqueness. And let’s not forget the wow-factor that makes for that killer app.

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